diff --git a/et_rpc/rpc.go b/et_rpc/rpc.go
index d6ac040..60843a4 100644
--- a/et_rpc/rpc.go
+++ b/et_rpc/rpc.go
@@ -9,6 +9,11 @@ const (
 	NodeState_Unhealthy
 )
 
+const (
+	RPCReply_Success RPCReplyCode = iota
+	RPCReply_Failure
+)
+
 type NodeArgs struct {
 	ID           string
 	Addr         string